Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/98

Click to flip

98 Cards in this Set

  • Front
  • Back
What is the procedure to empiric therapy?
Clindamycin + gentamicin(effective against gram-(+) or imipenem/cilastin(single broad-spectrum antibiotic) ->culture bug -> use specific drug last
What are the drugs used in Empiric therapy?
Clindamycin + gentamicin or imipenem/cilastin
Define: chemotherapy
The use of chemical s against invading organisms (invading bacteria); NOTE: term is used for both treatment of infection and cancer
Define: antibiotic
Chemical that is produced by a microorganism and has the ability to harm other microbes
Define: selective toxicity
The ability of a drug (chemical) to injure a target cell or organism without injuring other cells or organisms that are in intimate contact
How do u select the most appropriate anti-microbial agent?
1. Organisms identity and its sensitivity to a particular agent, 2. site of infection, 3. safety of the agent, 4. patient factors, 5. cost of therapy
Define: empiric therapy
Use of antimicrobial agents before the pathogen is known; based on experience; justified if evidence demonstrates that early intervention will improve outcomes
What is the most commonly used method to test susceptibility to antibiotics
Disk diffusion test - disks containing antibiotics are placed on culture dishes inoculated w/the microorganism to be tested. Growth = resistance to bugs, no growth = sensitivity to bug
Define: selective toxicity
Kill the germs not the patient -> achieved by disruption of cell wall, protein synthesis, enzyme unique to bacteria
What are the characteristics of selective toxicity?
1. Unique target must be present in pathogen + absent in host, 2. Target must be structurally different in pathogen vs host, 3. Target must be more important in pathogen than in host
What is the MOA of disruption of the bacterial cell wall
Bacteria are encased in a rigid cell wall -> if disrupted bacteria would absorb water, swell, burst
Which drugs target microbes cell wall -> thus promoting bacterial lysis?
Penicillin and cephalosporins; b/c mammalian cells have no cell wall -> drugs directed at this structure do not affect the host
What is the MOA of inhibition of an enzyme unique to bacteria
Bacteria need to produce folic acid denovo -> sulfonamides inhibit bacteria production -> no PABA -> folic acid -> no division
What drug inhibits bacterial de novo generation of folic acid?
Sulfonamide
What is the combination of drugs to target folic acid production?
Sulphonamides(inhibits dihydropepteroate synthase) + trimethoprim(inhibits dihydrofolate reductase)
What drugs cause disruption of cell wall membrane?
Amphotericin B, ketoconazole
What drugs cause bacteriostatic inhibitors of protein synthesis?
Clindamycin, erythromycin, tetracyclines
What drugs cause interference w/synthesis of bacterial DNA or RNA
Fluoroquinolones, rifampin
What drugs are anti-metabolites
Flucytosine, sulfonamides, trimethoprim
What drugs are viral enzyme inhibitors
Acyclovir, zidovudine, saquinavir, indinavir
What drugs are mycolic acid synthesis?
Isoniazid
What drugs have unknown mechanisms
Amntadine, ethambutol, pyraziamide
What drug is involved in the blockage of DNA twisting?
Fluoroquinolones - thus blocks DNA gyrase from working
What is the MOA of "unique" selective targeting?
Drug targets genetic or biochemical pathway that is unique to pathogen(ie bacterial cell wall synthesis inhibitors)
What is the MOA of "selective" selective targeting?
Drugs targets protein isoform that is unique to pathogen(ie DHFR inhibitor)
What is the MOA of "common" selective targeting?
Drug targets metabolic requirement that is specific to pathogen(ie 5-Fluorouracil)
Drugs that affect growth
Bacterial static(tetracycline)
Drugs that kill off the bactera
Bacterialscidal(penicillin)
What are the bactericidal drugs that we need to know?
1. Bacitracin, 2. beta-lactams, 3. quinolones, 4. aminoglycosides, 5. polymyxins, 6. rifampin
What are the bacteriostatic drugs that we need to know?
1. Tetracycline, 2. sulfonamide, 3. trimethoprim, 4. chloramphenicol, 5. macrolide, 6. novobiocin, 7. clindamycin
Define: minimum inhibitory concentration
Anti-microbial should be present in concentrations such that it can either inhibit bacterial growth
Define: minimum bactericidal concentration
Kill the organism
What are 3 factors that determine susceptibility and resistance of microorganisms to antimicrobial agents?
1. Failure of drug to reach its target, 2. drug inactivation, 3. target alteration
What is the MOA of entry for slow drug entry into a bacteria?
Slow drug entry into a cell = via PORINs
What is the MOA of gentamicin
Targets ribosome -> actively transported across the cell membrane
What is the MOA of resistance of gentamicin?
1. Bacteria makes resistance by mutating the active transport mechanism of the drug, 2. anaerobic conditions slows entry into the cell
What is the MOA of resistance of tetracyclines, chloramphenicol, fluoroquinolones, macrolides, beta-lactam antibiotics.
Bacterial efflux pumps -> transports drugs out
How do bacteria prevent entry of a drug into the cell?
1. Mutation of porin causes blockage thus drug cant get in, 2. mutation in transport mechanism(active transport - gentamicin, efflux pump - tetracycline)
How do lower urinary tract antibiotics get to its target site?
The antibiotic is NOT metabolized in the body -> goes thru the blood -> into urine (intact) -> has effect
How do bacteria inactivate aminoglycosides + beta-lactam antibiotics?
Production of enzymes that modify or destroy the antibiotic (aka anti-penicillin protein)
What drug is a prodrug that requires a bacterial enzyme to activate the drug?
Isoniazid - mycobacterium tuberculosis activates the drug inside the bacteria(the bug is its own worst enemy)
What is the MOA of Fluoroquinolones resistance?
Utilizes mutation of natural target - gyrase mutation
What is the MOA of macrolide and tetracycline resistance?
Target modification - ribosomal protection
What is the MOA of resistance of staphylococcal resistance to methicillin?
Acquired resistant form of the susceptible target -> caused by production of low-affinity penicillin binding proteins(ie penicillin cant work on its target)
Define: vertical acquisition of drug resistance
Passage of trait to daughter cells
Define: horizontal acquisition of drug resistance
Between individual s by PLASMID EXCHANGE
What are the advantages of horizontal gene transfer in bacteria?
1. Avoids lethal mutation of essential genes, 2. level of resistance is higher -> caused by incremental change, 3. genes can be transferred to susceptible cells easily
What is the MOA of streptomycin resistance?
Ribosomal mutation
What is the MOA of rifampin resistance?
RNA polymerase mutation
What is the MOA of linezolid resistance?
Ribosomal RNA mutation
How does high level resistance to a drug emerge?
1. Sequential series of mutations(plasmids), 2. mutation that confers high-level resistance in a single step
What is horizontal gene transfer
Plasmid transfer of resistant genes
Define: conjugation
Direct transfer of resistant genes by cell-to-cell contact through a sex pilus or bridge(occurs in gram (-) bacilli + enterococci + staphylocicci)
What is the requirements in bacteria that can under conjugation?
R-factor
How is antibiotic resistance is enhanced by natural selection
Top selection (mixed resistance population) -> middle selection (only the strong survive) -> last selection -> only the strong replicate
What is strep pneumoniae resistant to?
Penicillin
What is e coli resistant to?
Fluoroquinolone
What is staph aureus resistant to?
vancomycin
What is the problem w/broad spectrum antibiotics
Sine broad spectrum antibiotics kill off more competing organisms than do narrow-spectrum drug, emergence of resistance is facilitated most by the broad-spectrum drugs
Define: superinfection
New infection that appears during the course of treatment for a primary infection -> new infection can develop b/c antibiotic use can eliminate the inhibitory influence of normal flora -> allowing a second infectious agent to flourish (common in broad-spectrum agents)
How do you select antibiotics
1. Identify organism, 2. drug sensitivity, 3. host factors
What type of drugs are used to keep bacteria at bay in AIDS patients?
Bactericidal
How does meningitis impede drug access?
BBB
How does endocarditis impede drug access?
Bacterial vegetation in the heart are difficult to penetrate
How does infected abscesses impede drug access?
Poor vascularity and the presence of pus and other material
What are the 3 ways to get a drug across the BBB?
1. Drug that readily crosses the BBB, 2. inject into subarachnoid space, 3. remove pus that hinders drug access
Why do the elderly have high drug sensitivity?
Reduced rates of drug metabolism + excretion -> leads to accumulation of antibiotics to toxic levels
Why do neonates have high drug sensitivity?
Poorly developed kidney and liver function -> eliminate drugs slowly
What is the side effect of sulfonamides in newborns?
New borns + sulfonamides = kernicterus(high levels of bilirubin)
What is the side effect of tetracyclines in new borns?
Binds to developing teeth -> causes discoloration of the teeth
What is the side effect of gentamicin during pregnancy?
Pregnancy + gentamicin -> irreversible hearing loss
What is the side effect of anti-microbial drugs during pregnancy?
Pregnancy + antimicrobial -> crosses placenta -> posing a risk to the developing fetus
What is the side effect of tetracyclines during pregnancy?
Pregnancy + tetracycline -> hepatic necrosis, pancreatitis, renal damage
What is the side effect of sulfonamides in breast milk?
Sulfonamide + breast feeding -> enters breast milk
Which antibiotics have a chance of severe allergic reaction
1. Penicillin, 2. sulfonamide, 3. trimethoprim, 3. erythromycin
What is the side effect of sulfonamides in G6PD deficient people?
Hemolysis
What are the reasons to use anti-biotic combinations?
1. Initial therapy of severe infection, 2. mixed infection, 3. prevention of resistance, 4. ↓ toxicity, 5. enhanced anti-bacterial action
What are the 3 possible effects by using 2 antibiotics in combination?
1. Additive, 2. potentiative(aka synergistic), 3 .antagonistic(static agent is antagonistic to cidal agent
What is the MOA of an additive response?
Antimicrobial effect of combination = the sum of the effects of the two drugs alone(ie 2 bacteriostatic agents w/same MOA)
What is the MOA of a potentiative (synergistic) response?
Effect of the combination is greater then the sum of the effects of the individual agent(shows a 4x ↑ in antibacterial activity aka ↓ in MIC by 1/4)
What are the 3 mechanisms of antibiotic synergism?
1. Blockade of sequential steps(trimethoprim + sulfamethoxazole, 2. inhibition of enzyme(beta-lactam + beta-lactamase inhibitor sulbactam), 3. enhancement of AB uptake(penicillin ↑ uptake of aminoglycoside)
Define: mixed infections
Infections that may be caused by more than one microbe -> common in brain abscesses, pelvic infection, and infections from perforation of abdominal organs.
How does the combination of flucytosine + amphotericin B work?
Decreased toxicity -> treats fungal meningitis (prevents risk of amphotericin-induced damage to kidney)
How does the combination of penicillin + aminoglycoside work?
Enhanced antibacterial action - penicillin weakens bacterial wall + aminoglycoside suppresses protein synthesis
When do u use prophylactic antibiotics?
Surgery, congentital abnormalities, neutropenia
What are the misuses of antibiotics
1. Viral infection, 2. fever of unknown origin, 3. improper dosage
What group of drugs is amoxicillin in?
Penicillins
What group of drugs is tetracycline in?
Tetracyclines
What group of drugs is streptomycin in?
Aminoglycosides
What group of drugs is levofloxacin in?
Quinolones
What group of drugs is cefaclor in?
Cephalosporins
What group of drugs is erythromycin in?
Macrolides
What is the MOA of amoxicillin?
Binds to Penicillin binding proteins
What is the MOA of tetracycline?
30S ribosome
What is the MOA of sterptomycin?
Affects protein synthesis
What is the MOA of levofloxacin?
DNA gyrase inhibitors
What is the MOA of cefaclor?
Protein synthesis
What is the MOA of erythromycin?
50S ribosome